I have spent the last couple of days reading the info over at https://www.pavingexpert.com/block-paving with particular emphasis on Paving over an existing surface within the faq's as I want to relay the block paving driveway on an ex-council property I have just purchased.
I have a reasonable understanding of block paving construction but this particular driveway has been giving me some concerns.
The driveway is over 20 years old and has been very poorly installed. It has been laid on top of multiple layers of old concrete slabs with a grit bed, and has no sub-base or sand bed.
Photo of the construction below:-
I was thinking of removing the paving, grit, and the first layer or two of the old slabs to give me adequate depth for an approx 150mm type 1 sub base and a 50mm sand bedding, however, it is obvious that the slabs below will be in poor condition and badly settled.
My plan was to compact the type 1 sub-base in multiple layers, hoping that this would fill any cracks in the old surface. Before proceeding I have done some reading and I am now concerned that the old slabs could still move or settle and have an impact on any new paving.
I was also thinking of possibly building a block retaining wall to support and hide the exposed slabs, I have marked up the image below to show this:-
So basically my questions are:-
1. Is it possible to 'revive' this driveway without removing all of the old slabs? I don't want to have to remove all of the old slabs as it will result in my sub-base costing a fortune. I would rather try and work with the existing slabs, if possible.
2. Would the retaining wall I have suggested in the image above be beneficial?
I have also attached another couple of images below to give a better idea of what I am working with.
1 - No: it all neds to come up and be built "from scratch".
2 - not only 'beneficial' but *essential*. A flag-on-edge ( https://www.pavingexpert.com/featur06 ) may well be sufficient, but you most definitely need some form of retaining structure.
Tony McC wrote:1 - No: it all neds to come up and be built "from scratch".
2 - not only 'beneficial' but *essential*. A flag-on-edge ( https://www.pavingexpert.com/featur06 ) may well be sufficient, but you most definitely need some form of retaining structure.
Tony,
Thanks for your response, much appreciated.
I’m not surprised I have to tear it up, but at least its just lifting some slabs and not a full excavation.
When I remove the block paving and slabs I will have around 400mm depth to build up, 100mm of this will be the paving and bed. Would it be ok to bring up the first 150mm in subsoil with a membrane to reduce the amount of type 1 required?
Hire a concrete crusher and save a fortune on disposal as well as type 1. I crushed my old patio foundations. The hard work was pulling up the old foundations but the crushing was easy. I’m in Hertfordshire and hired a crusher from one of the contributors to this forum - Dig Dug Dan. Why pay for a grabber to take your old foundations away then pay someone else to deliver new crushed material.
Dan deserves a medal for all the money he has saved Brew Cabin readers over the years - using a crusher is a really good idea.......whereas building up layers using salavaged sub-soil is a really bad idea, really, really bad.
If you need to build-up, look for a cheaper crushed aggregate. This might be crushed concrete/brick, or a 50mm crusher run, or a Type 2 aggregate. Place, spread and level in layers of not more than 150mm and thoroughly compact before placing subsequent layers.
Sub-soil is too unpredictable and too difficult to compact thoroughly. It's rarely worth spoiling the ship for a ha'p'orth of tar, and the few quid it would cost to bring in build-up aggregates will more than pay for itself in peace of mind.
Crushing the slabs is a great idea and definitely what I will do. I do not know why I never thought of this as I occasionally see groundworkers crushing demo material for use under roads, footpaths etc on site.
Unfortunately for me I live in Scotland, so maybe a bit far for Dig Dug Dan!
